Plug Assembly for Borescope Port Cooling

ABSTRACT

A removable plug assembly modified for port cooling plugs a borescope port but allows controlled leakage to cool surfaces adjacent the port below oxidation limits. The plug assembly has a plunger and plug wherein the plug includes a plurality of flow recesses allowing bypass air to cool the surface having the port, as well as the borescope plug.

BACKGROUND

Present embodiments relate generally to a gas turbine engine. More specifically, the present embodiments relate to a modified borescope plunger which provides borescope port cooling.

In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases which flow downstream through turbine stages. These turbine stages extract energy from the combustion gases. A high pressure turbine first receives the hot combustion gases from the combustor and includes a stator nozzle assembly directing the combustion gases downstream through a row of high pressure turbine rotor blades extending radially outwardly from a supporting rotor disk. In a two stage turbine, a second stage stator nozzle assembly is positioned downstream of the first stage blades followed in turn by a row of second stage rotor blades extending radially outwardly from a second supporting rotor disk. This results in conversion of combustion gas energy to mechanical energy.

The first and second rotor disks are coupled to the compressor by a corresponding high pressure rotor shaft for powering the compressor during operation. A multi-stage low pressure turbine may or may not follow the multi-stage high pressure turbine and may be coupled by a second shaft to a fan disposed upstream from the compressor.

As the combustion gas flows downstream through the turbine stages, energy is extracted therefrom and the pressure of the combustion gas is reduced. The combustion gas may continue through multiple low stage turbines.

The annular nozzle assembly is formed of a plurality of nozzle segments which are joined at circumferential ends of the segments. Each high pressure turbine nozzle includes vanes which are hollow and receive a portion of pressurized cooling air from the compressor to cool the vanes during operation. A portion of the vane air is then channeled radially inwardly from a radially outer band or wall through the vane to the inner band or wall.

High pressure turbine components must be cooled to meet strength and endurance requirements due to the high gas path temperatures characteristic to this region of the engine.

In order to periodically inspect the condition of the core parts of the engine, such as the combustor, compressor and turbine blades and nozzle assembly borescope ports are provided in engine casings and frames. This allows optical borescope instruments to be inserted into the core engine to enable visual inspection of the condition of these parts without having to disassemble the gas turbine engine.

During operation, borescope plugs are utilized to close and seal these ports preventing mixture of bypass or cooling air with combustion gas having a much higher temperature. Due to the high operating temperature of the combustion gas passing over the nozzle toward the turbine blades, the nozzle operating surfaces can deteriorate due to metal oxidation caused by the high operating temperature. This may cause shortened turbine life, premature turbine removal and excessive field service. Additionally, the borescope port may also be distressed.

It would be desirable to reduce or eliminate the nozzle distress caused by operating temperatures exceeding the oxidation limits for this portion of the turbine. It would additionally be desirable to reduce distress of the borescope port to also reduce or limit oxidation problems. It would be desirable to reduce the temperature localized of the stage one nozzle components and extend the life of at least this portion of the turbine.

SUMMARY

A removable plug assembly modified for port cooling comprises a plunger having a first end, a second end and shaft defined therebetween, a sealing plug at the second end of the plunger having a first diameter, the plug having a tapered surface tapering to a second diameter which is less than said first diameter, a plurality of flow recesses along an outer surface of the plug between at least one surface of the first diameter and at least one surface of the second diameter, the flow recesses allowing by-pass air to reach a surface wherein a port is disposed. The plug assembly could be utilized in a plurality of ports utilized for inspection within a turbine engine.

All of the above outlined features are to be understood as exemplary only and many more features and objectives of the plug assembly for borescope port cooling may be gleaned from the disclosure herein. Therefore, no limiting interpretation of this summary is to be understood without further reading of the entire specification, claims, and drawings included herewith.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

The above-mentioned and other features and advantages of these exemplary embodiments, and the manner of attaining them, will become more apparent and the nozzle feature will be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side-section view of an exemplary gas turbine engine.

FIG. 2 is a side-section view of the turbine area of the gas turbine engine.

FIG. 3 is an isometric view of an exemplary plug assembly.

FIG. 4 is a detail isometric view of the lower portion of the plug having a plurality of flow recesses.

FIG. 5 is a detail section view of a plug installed in an exemplary nozzle.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments provided, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation of the disclosed embodiments. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to still yield further embodiments. Thus it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Referring to FIGS. 1-5, various embodiments of a gas turbine engine are depicted having a borescope plug assembly which provides borescope port cooling as well as cooling of operating surfaces of a turbine nozzle. The borescope assembly includes a plug having a plurality of flow recesses allowing controlled leakage of bypass air from the bypass duct side of the nozzle to the combustion gas side of the upper wall of the nozzle, for example a first stage nozzle within the turbine. Additionally the cooling air allows cooling for a borescope port so that the oxidation limits are not reached for the nozzle surface or the borescope port.

The terms fore and aft are used with respect to the engine axis and generally mean toward the front of the turbine engine or the rear of the turbine engine in the direction of the engine axis, respectively. The term radially is used generally to indicate a direction perpendicular to an engine axis.

Referring now to FIG. 1, a schematic side section view of a gas turbine engine 10 is depicted. The exemplary gas turbine engine 10 may be used in a variety of areas including aviation and in marine and industrial areas to power ships, pump oil, compress gas, produce energy or the like. The engine 10 is axis-symmetrical about a longitudinal axis or centerline 22 and includes at a forward end an inlet 12, a fan 18 and/or low pressure compressor, depending on the desired use of the turbine engine 10. Following the low pressure compressor or fan 18, air moves through a high pressure compressor 14 wherein air may be further pressurized. Moving aft, downstream of the compressor 14 the pressurized air is used mixed with fuel for combustion or is used in cooling circuits in the gas turbine engine, generally referred to as by-pass air. In the combustor 16 the pressurized air is mixed with fuel and ignited creating a hot combustion gas 24 which is discharged from the combustor 16 through at least a high pressure turbine 20. The high pressure turbine 20 may be, for example, a two-stage high pressure turbine. Each stage includes a nozzle stator assembly 26 extending about the axial centerline 22 in a circumferential direction.

The nozzle stator assembly 26 is depicted generally and indicates where the exemplary embodiments of the plug assembly are located in the exemplary gas turbine engine 10. However, one skilled in the art will understand the plug assembly may be used in other areas of the engine 10 including, but not limited to, the high and low pressure compressors 14, 18, the low pressure turbine 21 and any other area where temperature oxidation limits may be breached.

Referring now to FIG. 2, a side-section view of the high pressure turbine 20 is depicted. The turbine area is represented by two ducts, a combustion gas duct 23 and a bypass air duct 27 spaced radially outward from the combustion gas duct 23. The combustion gas duct 23 receives combustion gas 24 from the combustor 16 and the combustion gas 24 passes by a first stage nozzle assembly 26 and through a rotor assembly comprising a rotor 38 and a turbine or rotor blade 39. This rotor assembly is connected to a shaft, rotating about axis 22, extending from the turbine 20 forward to the high pressure compressor 14 (FIG. 1). The first stage nozzle 26 is defined by a nozzle outer wall 28, a nozzle inner wall 30 and a stationary vane 32. The terms inner and outer are referenced relative to radial direction and the axis 22. The nozzle outer wall 28 includes a lowermost surface 34 which is an operating surface within the duct 23 and exposed to the high temperature combustion gas 24. A port 36 is located in the nozzle outer wall 28 and passes through the lower surface 34. The port 36 allows insertion of a borescope during maintenance periods in order to inspect internal portions of the turbine or other core elements.

Above the duct 23 is a bypass air duct 27 through which bypass air 25 passes. The bypass air has a lower temperature than the combustion gas and is utilized for various purposes including, but not limited to, cooling of core elements, such as the first stage nozzle 26. Above the duct 27 is a combustor outer casing 31 which includes a port 33.

As previously indicated, the port 33 and port 36 are utilized during maintenance to examine the internal core elements of the gas turbine engine 10. The ports 33, 36 currently depicted are utilized to inspect the turbine 20 for maintenance purposes. However, the borescope ports and plugs discussed herein are not limited to turbines but may be utilized at various areas of the turbine engine 10.

Referring still to FIG. 2, a borescope plug assembly 40 is shown in the turbine 20. The assembly 40 includes a first end 42 and a second end 44 located generally at the first stage nozzle 26. The first end 42 is fastened to the combustor outer casing 31 in order to install the borescope plug assembly 40 to the combustor outer casing 31. The fastening structure may vary but according to the instant embodiment, a threaded fastening engagement is utilized. However, alternate structures may be used. Oppositely, the second end 44 of the assembly 40 is positioned in the port 36 of the nozzle outer wall 28. The borescope plug assembly 40 includes a plunger 50 and a plug 52. The plunger 50 includes a shaft or body 54 which extends from near the first port 33 to the lower nozzle port 36. The plunger 50 includes an upper end 56 and a lower end 58 where the plug 52 is positioned. At the upper end 56 is a washer 60 and a ball bearing 62 through which the plunger 50 passes. The ball bearing defines a pivot point for the assembly 10. The plunger 50 may include a housing 64 or other structure outside of the shaft 54.

At the lower end of the plunger 50 is plug 52 which is named for its function to plug the nozzle port 36. The plug 52 blocks the majority of bypass air 25 from leaking to the combustion duct 27 but as explained before allows some controlled leakage. This bypass air leaks to the surface 34 of the nozzle assembly 26 to cool the port 36 and the nozzle surface 34.

Referring now to FIG. 3, an isometric view of the borescope plug assembly 40 is depicted. The borescope plug assembly 40 more clearly depicts the plug 52 connected to the plunger 50. The plug 52 includes a tapered surface 70 extending from an outer diameter of the plug 52. The tapered surface 70 seals along a corresponding surface to the port 36. The outer diameter 72 closely approximates the port 36 diameter. Thus the tapered surface is seated in the port providing a seal and inhibiting uncontrolled leakage of bypass air across the port. Through the tapered surface 70, the plug changes to a smaller base diameter 74. The base diameter has a tip 76 extends some axial distance according to the instant embodiment. However, various shapes may be utilized. Extending along the outer surface of the tip 76 and up the tapered surface 70 are a plurality of flow recesses 80.

Referring now to FIG. 4, the recesses 80 are shown more clearly. The recesses 80 comprise a first leg 82 which extends along the tapered surface 70 from the outer diameter 72 and a second leg 84 which extends from the lower end of the tapered surface 70 along the tip 76. The first legs 82 are at an angle to the axial direction of the plunger 50. The second legs 84 are parallel to the axial direction. Each of the recesses 80 comprise a first end 86 and a second end 88 allowing cooling air above the sealing surface 70 to pass through the sealed area 70 toward the combustion gas duct 23. The tip 76 is located in or around the lower surface 34 of the nozzle outer wall 28 (FIG. 2). Thus, the bypass air 25 can pass through the recesses 80 from the cool air side to the hot air side of the combustion gas duct 24 (FIG. 2). This is effectively a controlled leakage which allows the outer surface 34 of the nozzle assembly 28 to be cooled to a local temperature below oxidation limits. As a result, the lifespan of the nozzle assembly 26 or other cooler elements utilizing this design may be increased. This will result in less down time for the turbine engine due to disassembly of the turbine engine 10.

The recesses 80 may have various cross-sectional shapes. The exemplary embodiment utilizes an elliptical recess shape. However, circular or other shapes may be utilized as desired. Additionally, the recesses 80 may be sized to control flow rates and thus limit usage of bypass air to desirable amounts. For example, during design of one exemplary embodiment, flow apertures in the nozzle assembly 26 were eliminated. These apertures had a preselected total surface area which resulted in a determinable flow rate of bypass air. Accordingly, the recesses 80 were sized to have an equivalent total flow area in order to approximate a similar or equivalent flow volume or flow rate of bypass air. Various methods may utilize to determine flow rate or sizes in order to adjust the amount of bypass air utilized in this endeavor.

As depicted, the embodiment shows that the recesses extend linearly in segments or legs. However alternate embodiments may be utilized. For example, the legs of the recesses 80 may approximate a curve around the surface(s) of the plug 52. Alternatively, rather than linear segments, the recesses may extend in a curve about the plug 52. The curve or linear segments approximating a curve may be continuous or a plurality of discontinuous lengths to form one or more helical or other shapes. It should be understood that various shapes may be utilized other than linear segments or arrangements.

Referring now to FIG. 5, a detailed side-section view of the plug assembly 40 in the first stage nozzle 26 is depicted. The bypass air 25 is shown passing through the recesses 80, to cool the inner surface of the outer wall 34. Thus, the lifespan of the nozzle 26 is extended by reducing temperatures below oxidation limits. As noted previously, the plug assembly 40 may be used for various ports including, but not limited to, the nozzle port described.

While multiple inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the invent of embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

Examples are used to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the apparatus and/or method, including making and using any devices or systems and performing any incorporated methods. These examples are not intended to be exhaustive or to limit the disclosure to the precise steps and/or forms disclosed, and many modifications and variations are possible in light of the above teaching. Features described herein may be combined in any combination. Steps of a method described herein may be performed in any sequence that is physically possible.

All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.

It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.

In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03. 

What is claimed is:
 1. A removable plug assembly modified for port cooling, comprising: a plunger having a first end, a second end and shaft defined therebetween; a sealing plug at said second end of said plunger having a first diameter; said plug having a tapered surface tapering to a second diameter which is less than said first diameter; a plurality of flow recesses along an outer surface of said plug between at least one surface of said first diameter and at least one surface of said second diameter; said flow recesses allowing by-pass air to reach a lower surface wherein a port is disposed.
 2. The removable plug assembly of claim 1, said plug disposed in a port for a borescope.
 3. The removable plug assembly of claim 1, said assembly passing through a first wall.
 4. The removable plug assembly of claim 3, said first wall being a combustor casing.
 5. The removable plug assembly of claim 3, said assembly passing through a second wall.
 6. The removable plug assembly of claim 5, said second wall being a turbine casing.
 7. The removable plug assembly of claim 1, said first end of said plunger passing through a bearing.
 8. The removable plug assembly of claim 1, said second diameter having a thickness in an axial direction.
 9. The removable plug assembly of claim 1, said flow recesses extending through at least one surface.
 10. The removable plug assembly of claim 1, said flow recesses extending through two surfaces.
 11. The removable plug assembly of claim 1, said flow recesses extending through three surfaces.
 12. The removable plug assembly of claim 1, said flow recesses having a first leg and a second leg.
 13. The removable plug assembly of claim 12, said first leg being at an angle to an axis of said plunger.
 14. The removable plug assembly of claim 12, said second leg extending in an axial direction.
 15. A removable plug assembly, comprising: a plunger having an upper end, a lower end and a shaft therebetween; a sealing plug at a lower end of said shaft said plug having a sealing surface therealong and plurality of flow recesses along said sealing surface; said plurality of flow recesses allowing by-pass air to move from a first end of said sealing surface to a second end of said sealing surface.
 16. The removable plug assembly of claim 15 wherein said flow recesses are formed by at least one linear segment.
 17. The removable plug assembly of claim 15 wherein said flow recesses are curved about said sealing surface.
 18. The removable plug assembly of claim 15 wherein said flow recesses are formed of linear segments.
 19. The removable plug assembly of claim 15 wherein said sealing surface is tapered from a first diameter to a second diameter.
 20. A removable plug assembly allowing for port cooling, comprising: a plunger for positioning within a borescope port of a gas turbine engine; said plunger having a first end, a second end and a shaft therebetween; a plug disposed at said second end of said shaft, said plug having a first diameter disposed on a first side of said port, a second diameter passing into said port and a tapered surface therebetween; said plug further comprising a sealing surface to engage said port; at least one flow recess extending from said first side of said portion to said second diameter on a second side of said port allowing cooling air to pass along said tapered surface. 